Aircraft air pump



Sept. l, 1942. R. R. CURTIS :JAL

AIRCRAFT AIR PUMP 2V Sheets-Sheet 1 Filed Feb. 29, 1940 Nm. N

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Sept. l, 1942'. R. R. CURTIS ITAL AIRCRAFT vAIR PUMP Filed Feb. 29, 1940 2 Sheets-Sheet 2 s. my, o; w mn. Mm www m h ,3% @n 'ywheel effect as it may have.

Patented sept. 1, '1942 AIRCRAFT AIB PUlVIP Russell B. Curtis, Dayton, and Theodore R. Thoren, Bedford, Ohio, assignors to Curtis Euhrinp Company, Dayton, Ohio, a corporation of Application February 29, 1940, Serial No. 321,494

(ci. vs4-1.5)

l Claims.

'I'his invention relates to air pumps and has special reference to air pumps for aircraft. Most modern aircraftemploy a pump, usually of the rotary sliding vane type to provide air under pressure for operating de-icing equipment, and air under vacuum fo'rv operating flight instruments, etc.

One of the main considerations in the design of aircraft engines is lightness and therefore aircraft engineers prefer' to employ no flywheel to smooth out the separate impulses in the cylinders, depending rather on the propeller for such 'I'he result is that the engine crankshaft is subject to slight change in angular velocity a't as many points in a single revolution as there are impulses, this effect being commonly referred toA as torsional whip. Variation in the intensity of the sveral impulses or defective firing in a cylinder may at times considerably` intensify this torsional whip.

Due to the same necessity for lightness as well as to space limitations, engine driven 'acessories are made as small and light as possible and then often loaded to near their maximum capacity. A heavily loaded pump, for instance, when driven by an engine having considerable torsional whip, puts a severe strain on the drive which connects the pump and engine, and it -follows that any drive which absorbs some or all of this torsional whip will be highly advantageous to the assembly.

When a pump is to be mounted on an aircraft engine and driven directly from one of its shafts,

slight misalignment of the engine and pump shafts will inevitably be present and it is thereshould preferably be'provided a seal to prevent leakage from the pump along the outside of the shaft,` and since conservation of 'space is-important, it is another object of the invention to conserve space by making Athe shaft hollow, then placing the drive within the shaft and the seal without the shaft, within the same axial di- .mensions Acarefully measured amount during the entire time that the :pump is under rotation, the meterling system being so combined with the seal as to require no extraspace in the structure.

Another object is to provide a pump structure having means whereby it is quickly and easily disassembled into its several parts so that renewal parts may be quickly substituted and repairs,readily made.

'I'hese and other objects and advantages will become more clearly apparent from the following means or its equivalent be embodied in the drive. A

Since the selected engine shaft from which the pump must' vbe driven may rotate oppositely in different makes of engines, it is essential that the pump and its drive will operate equally well in either direction of rotation.

-renewed parts of maximum strength and endurr ance, light weight and low cost and absorbing a minimum of space in the assembly.

Since -any power pump having rotatable elements necessarily has a rotatable shaft extending, to which the driving force is applied, there detailed description, reference being made to the drawings, wherein,

Fig. 1 isan axial section thru a rotary pump embodying the principles of the invention.

Fig. 2 is`a transverse section taken at 2-2 of Fig. 1 showing the means for retaining the driving shank in place.

Fig. 3 is a fragmentary side view of the outer end of the hollow rotor shaft.

Fig. 4 is an endview of the shaft shown in 1Fig. 12 is a right hand end view of the driving p ug.

several views of the drawings.

end view of the driving Like numerals refer to like parts thruout the t `shank and shaft' in assembled relation.

and shaft and The pump selected as lan illustrative embodimen't of the'invention comprises a housing 20 having a head 22 secured thereto by screws 24 and lock washers 28. The head 22 supports one of the rotor bearings and provides a pressure tight closure for the end of the casing.

A liner 28 is press fitted in the casing and has port openings extending thru it which communicate with suction and discharge ports in the casing, but since the design of the ports hasl no bearing on this invention they are omitted from the drawings.

vThe rotor body 30 has its axis offset with rel equally spaced slots v42 into which two thru vanes 44 are slidably fitted. The two vanes'are alike, one being turned end for end with respect to the other and` positioned ninety degrees rotation therefrom. -The type ofv vane and their number intermediate the notches 10. Around porti 85 of the driving shank 84 is made sumciently` smaller than the hole in the shaft 38 to x the mazdmum misalignment of the shaft and at a predetermined'value.

The outer end 88 of the shank 84 is provided with external splines 88 adapted to iit slidably into a corresponding internally splined opening in the end of the engine shaft. The ilange-80 of the body 20 may be bolted or similarly secured to a mounting pad on the engine. t

The means provided for sealing against leakage from the drive end of the pump comprises several non-rotative andseveral rotative members. The vmetal seal cap 82 is press fitted to the body 20, a metal ring 84 ts the. body 20 freely,

and a synthetic rubber washer 98 is interposed between the two parts to seal against leakage which might occur around'the outside of ring 1 94, between parts 84 and 82 and then thru the inside of cap 92.

The cap 82 is counterbored to receive the small hub 88 which is molded as an integral part of the rubber washer 98. The ring 84 is counterbored for the small tube |00 which is press fitted in the ring and extends first tightly thru the hub 98 then slidably into a hole in the cap 82,

is selected for illustrative purposes only and is not intended as a structural limitation of thev invention.'

Press fitted into the hollow of the rotor driving shaft 88 is the driving plug 46 further secured against rotation in the shaft by the pin 48.' An integral driving hub 50 on the plug is of reduced diameter and provided with a, transversedriving slot 52 (see Figs. 11 and 12).

A driving spring 54, shown in detail in Figs'.

l. 8', 9 and 10, comprises, in a single piece, an endless loop formed into the shape of a double coiled helical spring wherein one coil 58 'lies between Athe other coil 58, the coilsbeing joined together at bothA ends to compose driving portions 80and 82 passing from theoutside of one coil to the outside of the other thru their' common axis.

A driving shank 84 (see Figs. 5, 6 and 7), has

' a-hub 88, substantially like the hub 50 of the driving plug 48, and having a like transverse slot 88. The driving portions 80 and 82 ofthe spring lie in the slots 52 andv 88 'and should be fitted to theslots closely.

The outer end ofthe hollow rotor shaft.

notches 10 (see Fig. 2). When the pump isbe- The ring 84 is therefore held nonlrotative by the tube |00, and since the ringiiits into the body 20 more closely than it does around the shaft 38, there is no possibility of the ring swinging with the tube |00 as an axis and dragging on the rotating shaft 88. n

Since synthetic rubber is subject to swelling under the action of oil and subject to flow under heavy pressure, a piloting end |02 extends from the ring 84 thru and beyond the inner diameter yof the rubber washer 88 to confine it toits allotted space.

l 'I 'he rotatable members of the sealing means g comprise a metal ring |04,l a synthetic rubber,

ring |08, a cup |08 and a spring ||0. 'I'he metal ring |04 is compelled to rotate with the shaft 88 98 (see Figs. 2, 3 and 4) is notched asl at 10 to provide the overload driving jaws 12. The driving shankv 84 has overload driving lu'gs 14 which are nor-` 'mally locatedvcircumferentially midway in the mg driven thru thespring u, the spring yields slightly and the lugs 14 move slightly closer to -one or the other of the edges of the jaws 12.

It is, however, only under-extreme overload conditions that the torsional deflection of the spring is suilicient to allow the lugs 14 to engage the J jaws 12in driving relation.

- Arcuate grooves 18 and 18 extend around the jaws 12 and lugs 14' respectively, and a snap ring 80 is sprung into these grooves to hold the The ring 80 is preferably fitted quite loosely in the grooves to allow slight misalignment of the re spective axes of the shaft and shank.

-One end of the ring 80 is bent over as at 82, (see Fig. 2) the bent over end extendinginto an appropriate notch 84 (see Fig. 4),'in the shaft,

thereby compelling unitary rotation'of the ring maintaining the shaft in the ring 'fi by a .pin ||2, one end of which is press tted into a hole in the shaft and the other end slidable in a, keyway ||4 in the ring. The rubber ring |08-fits overthe shaft 88 closely and' is confined to normal dimensions by the cup v| 08, the open side of which extends over the ring |04 but should not fit it too closely. 'I'he spring I8 abuts the inner member of the bearing 48, its expansive force acting against the cup |08 whereby .a seal is made betweenthe rubber ring |88 and shaft 88 and between the rubber ring andthe metalv ring |04, all of these parts rotating at the same speed. v

The rotatable metal ring |04, being movable axially, is therefore resiliently held in contact4 -withthe non rotatable metal ring 84 and it is important that their contacting faces each be finished to a mirror like surface to maintain a perfect seal under relative rotation.

Seals of this class, as customarily constructed,

-would have the non Vrotative ring 84 press tted. directly into the casing 2 0 and would, of course.

thereby eliminate the ring 88 by combining the 84 and cap 82'as one part.

' 'Where however. the non rotative 'ring is prees y fitted` into the casing, there is substantially a1; ways slight distortion of thev press tted ring,

which, alth'o practically unmeasurable, nevertheless manifests itself by slight leakage at the joint. y

The usual procedure is then to lap the rings |88 and s4 together 1n pme by rotation o: the ring |84 against the ring 84 with an abrasive lapping universal drive will be obvious.

is inactive. the lugs 14 of the drive shank 04 will compound therebetween. This procedure produces circular scratches which altho minute can never .be wholly eliminated by circular lapping.

Inasmuch as, Athe eiilcacy of the seal is in proportion to the perfection of the contacting surfaces of rotatable ring |04 with non rotatable ring 04, these surfaces, in the embodiment herein shown, are ground, lapped and honed to perfect mirror like planes separately and before assembly. and are not thereafter lapped one on the other by rotative movement therebetween, but

are instead lapped according to the well known.4

process of producing perfect plane surfaces which comprises movement of the part being lapped in constantly varying direction with respect to the plane surface lap.

Since, in the assembly, the rings |04 and 94 are resiliently held, neither being fitted closely to any other part so as to be distorted, it follows that the seal thus produced is substantially perfect under rotation.

In order to cause several of the seal members above described, to function also as a metering means for the pump lubricant, theend of the casing is provided internally with an annular groove I I6 to which oil under pressure is brought thru one of the small holes H8 or |20. The hole |20 communicates with a tapped opening |22 adapted for connection with the main oil pressure system ofthe engine by suitable piping,

be midway in the notches 10 (see Fig. 2) and when under normal load only slightly off the po-4 sition shown one way or the other depending on the direction of rotation. Underextreme overload condition, however, such as might inJure the driving spring 54 if much further increased, the lugs 14 of the drive shank will make contact with the jaws 12 of the rotor shaft and there will thenceforth be a positive drive as long as such overload conditions prevail.

When the device is once assembled as shown in Fig. 1, the entire rotor, drive and seal, with the exception of the cap 92 may be withdrawn from the casing 20 by merely removing the head 22, whereby worn or damaged parts may-be readily replaced or repaired. s

Having described an embodiment ofour invention in which the-objects h'ereinbefore set forth are achieved, we claim:

1. VA drive comprising a part tobe driven having an vaxially extending opening therein, a

diametrically slotted hub smaller than said opening and having an end portion nxed within the opening, a 'second diametrically slotted hub at the outer end of the opening, the hubs being axially spaced apart and th'e slots facing each other, a driving shank comprising a, prolongation on the second said hub adapted for conwhile the hole ||B is positioned to meet a cor-` responding hole in the mounting pad of the engine, the hole in the pad communicating with a vchamber in the engine which contains oil under pressure. A series of additional holes H8 are preferably provided so that the pump may be mounted inverted, or, turned ninety degrees either direction on its axis and in either case have a hole ||0 meet the hole in the engine 1mounting pad. The :press fit of the cap 02 into the body 20 closes the inside of the groove ||6 and converts it into a pressure tight annular channel.

A small passageway |24 lin cap 92 connects the annular channel IIB to the'end of the tube |00. the passage .way from the other end of the tube being prolonged by a hole V|26 which extends from the end of the tube to the Joint betweenizli non rotative 94 and the rotatable ring A raam opening |23 mtne rotatable ring |04 is connected -by ,a tiny metering hole |30 to the contacting surfaces betweenrings |04 and 04;

It will now be evident that there is only one joint in the sealing means' where there is relative rotation, and that there is a continuous supply of oil under pressure conveyed to this Joint from channel ||6 thru turbe |00 and hole |26, an'd that while the end of the hole |28 is kept closed by the rotating surface of ring |04 for the greater` portion of each revolution, a passage way for oil is nevertheless completed during about 256% of each revolution thru the meteringy hole |30 and radial hole |28 to the space |32 from which it finds its way thru the .bearing 40 to the blades 44 and rear bearing 38.

The hole |26 is made enough larger than the tiny metering hole |30, that should slight variance in the relative radial positioning of the two holes result from inaccuracies in manufacture,

'the percentage of time the oil passage 'is completed,v and consequently' the amount of1 oil' metered will not be seriously affected.

The advantage of the resilient whip absorbing When the device nection toa power source, a closed loop formed into a double coil spring wherein the turns of one coil are between the turns of the other and wherein integral ndiametricially extending driving ends connect the ends of the coils one to the other, said coils'. fitting loosely in saidv hollow and freely over said hubs, `and said driving ends fitting snugly in said slots, positive drive lugs extending radially from said shank into notches in said part, said lugs being circumferentially narrower than said notches and nor mally positioned midway therein, an annular groove partly in said driven part and partly in said lugs and a, spring snap ring in said groove.

2. A whip absorbing drive comprising an-elongated hollow member having peripheral notches at one end, a closure for the other end having a transverse driving slot opening toward the notched end of said hollow member, and endless coil spring within said hollow. member having looped ends one of which is seated within said driving slot, and a driving shank having a slot-A ted portion for receiving the 4other looped end of said spring and adapted for connection to ya power source, lugs on said shank extending into the notches in the end of said hollow member. said lugs being adapted to engage the notched end of said hollow member for positive drive when said spring has yielded to applied torque th'e radial slot in said one lug on the hollow member for maintaining said lugs in interengagement. l

4. A driving mechanism comprising va hollow "rotatable part, a. driven member fixed within` the hollow of said part and having a transversely slotted reduced hub portion, a driving member at one end of said hollow part having a tion, said driving member having a driving shank and a. radial iiange between the -driving shank and the end of the slotted hub portion, spaced axially extending interiitting means on said radial flange and said one end of the hollow part transversely slotted reduced hub portion within Y the hollow and facing said first slotted hub porproviding a positive drive between said driving y member and said hollow part when said means are in interengagement, and an endless coil coils connected to form driving portions, said ,the hollow having transverse slots `facing each y .spring vwithin said hollow part having its end f coils embracing said reduced hub portions andt-3 beingl driven thereby, circumferentially spaced intertltting lug means formed as longitudinal extensions on adjacent end portions of said driving member vand said driven hollow member and spaced radially outward of` said spring, said lug means being adapted to thrust against each other upon overloading `lof the torsion spring to directly couple said driving member and said driven hollow member together;

and means independent of said spring for limiting relatve endwise movements between said driving member and said driven hollow member.

7. A driving mechanism comprising a hollow rotatable member, a driven member fixed within the hollow of said rotatable-member and having a transversely slotted hub portion, adriving member at one end of said hollow rotatable member having a transversely slotted hub por- ,l spaced intertting lug means formed as longil other, one hub being secured within said hollow y part to rotate therewith and the other hub having a radially extending portion adjacent the slotted end thereof, a double coil spring fitting loosely within said hollow and over said slotted hubs and having end portions fitting snugly in said slots, spaced interfltting lug means on an end of said rotatable part and on said radially extending portion, aligned slots in said intertting lug means, and ring means in said aligned slots for limiting relative endwise movements of said other hub with respect to said hollow part;

6. A driving mechanism comprising a driving member, a torsion spring driven vby said driving member, a hollow member housing said spring tion within the hollow and facing the slotted hub on said driven member, said driving mem-v ber having a driving shank and a radial ange betweenthe shank and the slotted hub thereon,

tudinal extensions on said radial ange and said one end of the. hollow rotatable member providing a positive drive between said driving member and said hollow rotatable member when said lug means are in interengagement, and a torsion spring within said hollow rotatable member having the ends thereof formed to seat inthe slotted v hub portions of said driving and driven members providing a yieldable drive therebetween when v said interiittinglug means are in spaced relation,

and means for limiting relativeendwise movements between said hollow rotatable member and said driving member. Y

, RUSSELL R. CURTIS.

THEODORE R. THOREN. 

